Photoinduced quantum spin/valley Hall effect and its electrical manipulation in silicene

2017 ◽  
Vol 121 (20) ◽  
pp. 205106 ◽  
Author(s):  
Hairui Bao ◽  
Wenhu Liao ◽  
Xincheng Zhang ◽  
Hong Yang ◽  
Xuexian Yang ◽  
...  
Keyword(s):  
Hall Effect ◽  
Quantum Spin ◽  
Electrical Manipulation ◽  
Valley Hall Effect

scholarly journals Quantum spin-valley Hall effect in AB-stacked bilayer silicene

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kyu Won Lee ◽  
Cheol Eui Lee
Keyword(s):  
Hall Effect ◽  
Density Functional ◽  
Tight Binding ◽  
Quantum Spin ◽  
Chern Number ◽  
Antiferromagnetic Order ◽  
Gradual Change ◽  
Edge States ◽  
Binding Model ◽  
Valley Hall Effect

AbstractOur density functional theory calculations show that while AB-stacked bilayer silicene has a non-quantized spin-valley Chern number, there exist backscattering-free gapless edge states within the bulk gap, leading to a quantum spin-valley Hall effect. Using a tight-binding model for a honeycomb bilayer, we found that the interlayer potential difference and the staggered AB-sublattice potential lead to abrupt and gradual change of the valley Chern number from a quantized value to zero, respectively, while maintaining backscattering-free gapless edge states if the valley Chern number is not too close to zero. Under an inversion symmetry-breaking potential in the form of the staggered AB-sublattice potential, such as an antiferromagnetic order and a hexagonal diatomic sheet, a finite but non-quantized (spin-)valley Chern number can correspond to a quantum (spin-)valley Hall insulator.

scholarly journals Quantum spin/valley Hall effect and topological insulator phase transitions in silicene

2013 ◽  
Vol 102 (16) ◽  
pp. 162412 ◽  
Author(s):  
M. Tahir ◽  
A. Manchon ◽  
K. Sabeeh ◽  
U. Schwingenschlögl
Keyword(s):  
Phase Transitions ◽  
Hall Effect ◽  
Topological Insulator ◽  
Quantum Spin ◽  
Valley Hall Effect

scholarly journals A scheme to realize the quantum spin-valley Hall effect in monolayer graphene

Carbon ◽  
2016 ◽  
Vol 110 ◽  
pp. 304-312 ◽  
Author(s):  
S.K. Firoz Islam ◽  
Colin Benjamin
Keyword(s):  
Hall Effect ◽  
Quantum Spin ◽  
Monolayer Graphene ◽  
Valley Hall Effect

scholarly journals Spin-layer locking induced second-order nonlinear effect in centrosymmetric crystals

2020 ◽  
Author(s):  
Yanchong Zhao ◽  
Luojun Du ◽  
Jing Liang ◽  
Mohammad Bahramy ◽  
Mingwei Yang ◽  
...  
Keyword(s):  
Hall Effect ◽  
First Principles ◽  
Nonlinear Effect ◽  
Quantum Spin ◽  
Second Order ◽  
Inversion Symmetry ◽  
First Principles Calculations ◽  
Quantum Spin Hall Effect ◽  
Valley Hall Effect ◽  
Insight Into

Abstract According to the generally accepted nonlinear principles, second-order nonlinear effect (SONE) is strongly inhibited by the crystalline symmetries and thus can manifest only in non-centrosymmetric materials with broken global spatial inversion symmetry. In stark contrast, here we report the observation of direct-current (DC) related SONE, including circular and linear photogalvanic effects, in centrosymmetric bilayer and multilayer MoS2. In conjunction with relativistic first-principles calculations, we uncover that the observed DC-related SONE in inversion-symmetric MoS2 results from the localized electronic states and the locking of spin with the layer and valley pseudospins. Our results provide a new insight into nonlinear physics and would be applicable to other phenomena thus far believed to occur only in non-centrosymmetric systems, such as quantum spin Hall effect, valley Hall effect, piezoelectricity and unconventional Ising superconductivity.

Quantum 20/20

2019 ◽  
Author(s):  
Ian R. Kenyon
Keyword(s):  
Quantum Mechanics ◽  
Hall Effect ◽  
Particle Physics ◽  
Quantum Spin ◽  
Lessons Learned ◽  
Compact Stars ◽  
Einstein Condensation ◽  
Local Conservation ◽  
Variable Theory ◽  
Quantum Gauge Theory

This text reviews fundametals and incorporates key themes of quantum physics. One theme contrasts boson condensation and fermion exclusivity. Bose–Einstein condensation is basic to superconductivity, superfluidity and gaseous BEC. Fermion exclusivity leads to compact stars and to atomic structure, and thence to the band structure of metals and semiconductors with applications in material science, modern optics and electronics. A second theme is that a wavefunction at a point, and in particular its phase is unique (ignoring a global phase change). If there are symmetries, conservation laws follow and quantum states which are eigenfunctions of the conserved quantities. By contrast with no particular symmetry topological effects occur such as the Bohm–Aharonov effect: also stable vortex formation in superfluids, superconductors and BEC, all these having quantized circulation of some sort. The quantum Hall effect and quantum spin Hall effect are ab initio topological. A third theme is entanglement: a feature that distinguishes the quantum world from the classical world. This property led Einstein, Podolsky and Rosen to the view that quantum mechanics is an incomplete physical theory. Bell proposed the way that any underlying local hidden variable theory could be, and was experimentally rejected. Powerful tools in quantum optics, including near-term secure communications, rely on entanglement. It was exploited in the the measurement of CP violation in the decay of beauty mesons. A fourth theme is the limitations on measurement precision set by quantum mechanics. These can be circumvented by quantum non-demolition techniques and by squeezing phase space so that the uncertainty is moved to a variable conjugate to that being measured. The boundaries of precision are explored in the measurement of g-2 for the electron, and in the detection of gravitational waves by LIGO; the latter achievement has opened a new window on the Universe. The fifth and last theme is quantum field theory. This is based on local conservation of charges. It reaches its most impressive form in the quantum gauge theories of the strong, electromagnetic and weak interactions, culminating in the discovery of the Higgs. Where particle physics has particles condensed matter has a galaxy of pseudoparticles that exist only in matter and are always in some sense special to particular states of matter. Emergent phenomena in matter are successfully modelled and analysed using quasiparticles and quantum theory. Lessons learned in that way on spontaneous symmetry breaking in superconductivity were the key to constructing a consistent quantum gauge theory of electroweak processes in particle physics.

scholarly journals Ultrafast non-excitonic valley Hall effect in MoS2/WTe2 heterobilayers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jekwan Lee ◽  
Wonhyeok Heo ◽  
Myungjun Cha ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
...  
Keyword(s):  
Hall Effect ◽  
Quantitative Information ◽  
Exciton Energy ◽  
Electron Hole ◽  
Kerr Rotation ◽  
Polarized Electrons ◽  
Spatially Resolved ◽  
Long Valley ◽  
Bound Electron ◽  
Valley Hall Effect

AbstractThe valley Hall effect (VHE) in two-dimensional (2D) van der Waals (vdW) crystals is a promising approach to study the valley pseudospin. Most experiments so far have used bound electron-hole pairs (excitons) through local photoexcitation. However, the valley depolarization of such excitons is fast, so that several challenges remain to be resolved. We address this issue by exploiting a unipolar VHE using a heterobilayer made of monolayer MoS2/WTe2 to exhibit a long valley-polarized lifetime due to the absence of electron-hole exchange interaction. The unipolar VHE is manifested by reduced photoluminescence at the MoS2 A exciton energy. Furthermore, we provide quantitative information on the time-dependent valley Hall dynamics by performing the spatially-resolved ultrafast Kerr-rotation microscopy; we find that the valley-polarized electrons persist for more than 4 nanoseconds and the valley Hall mobility exceeds 4.49 × 103 cm2/Vs, which is orders of magnitude larger than previous reports.

scholarly journals Tunable quantum spin Hall effect via strain in two-dimensional arsenene monolayer

2016 ◽  
Vol 49 (5) ◽  
pp. 055305 ◽  
Author(s):  
Ya-ping Wang ◽  
Chang-wen Zhang ◽  
Wei-xiao Ji ◽  
Run-wu Zhang ◽  
Ping Li ◽  
...  
Keyword(s):  
Hall Effect ◽  
Quantum Spin ◽  
Spin Hall Effect ◽  
Two Dimensional ◽  
Quantum Spin Hall Effect ◽  
Quantum Spin Hall

scholarly journals Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength-Dependent Mapping

Nano Letters ◽  
2017 ◽  
Vol 17 (9) ◽  
pp. 5719-5725 ◽  
Author(s):  
Nicolas Ubrig ◽  
Sanghyun Jo ◽  
Marc Philippi ◽  
Davide Costanzo ◽  
Helmuth Berger ◽  
...  
Keyword(s):  
Transition Metal ◽  
Hall Effect ◽  
Transition Metal Dichalcogenides ◽  
Metal Dichalcogenides ◽  
Valley Hall Effect ◽  
Microscopic Origin
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